The standard technique for making circuit interconnections for semiconductor devices consists of bonding a wire, typically a gold or aluminum alloy wire, to an aluminum alloy bond pad on the semiconductor die. In the case of a gold wire, bond eventually results in an intermetallic structure of several possible phases, depending on time and temperature and dictated by diffusion behavior. The highest bond strength is obtained by maximizing the intermetallic coverage under the ball bond.
Clean surfaces, high temperatures, and the proper amount of pressure and mechanical scrubbing contribute to an optimum reaction between the gold and aluminum metals in the wire and bond pad. Ideally, a very short bonding time may be used to create the intermetallic bond between the surfaces. While satisfactory processes have been developed for many of the typical semiconductor devices, all of the processes, known as thermosonic bond processes, rely on elevating the temperature of the semiconductor device during the bonding process.
Unfortunately, micromechanical devices such as the Digital Micromirror Device (DMD) cannot tolerate the elevating temperature required by IC wire bonding processes of the prior art. Therefore, a room temperature wire bonding process is needed that will allow temperature sensitive devices such as the DMD to be fabricated without damaging the temperature sensitive structures.